The printing plate material for CTP, which is inexpensive, can be easily handled, and has a printing ability comparable with that of a PS plate, is required accompanied with the digitization of printing data. Recently, a thermal processless printing plate material which can be applied to a printing press employing a direct imaging (DI) process without development by a special developing agent or a versatile thermal processless printing plate material which can be treated in the same manner as in PS plates has been required.
As a thermal processless printing plate material, there is Thermo-Lite produced by Agfa Co., Ltd. In a thermal processless printing plate material, an image is formed according to a recording method employing an thermal laser emitting light with infrared to near infrared wavelengths. The thermal processless type printing plate material employing this recording method is divided into an ablation type printing plate material, a development-on-press type heat fusible image formation layer-containing printing plate material, and a phase change type printing plate material.
Examples of the ablation type printing plate material include those disclosed in for example, Japanese Patent O.P.I. Publication Nos. 8-507727, 6-186750, 6-199064, 7-314934, 10-58636 and 10-244773.
Examples of the development-on-press type heat fusible image formation layer-containing printing plate material include printing plate materials disclosed in for example, Japanese Patent Publication Nos. 2938397 and 2938398, in which hydrophobic thermoplastic polymer particles can be combined with one another by heat application. However, no reference is made to adhesion of the polymer particles to the support.
Examples of the phase change type printing plate material include those disclosed in for example, Japanese Patent O.P.I. Publication No. 11-240270. In the phase change type printing plate material, the hydrophilic layer contains hydrophobe precursor particles, which are not removed during printing, and the hydrophilic layer at exposed portions changes to be hydrophobic.
A planographic printing plate material employing heat melting particles with a melting point of from 40 to 150° C. having specific physical properties is disclosed (see for example, Japanese Patent O.P.I. Publication No. 2001-200059.). Most of the heat melting particles with that melting point disclosed in the patent document above have a relatively low molecular weight. The relatively low molecular weight particles are poor in poor abrasion resistance, water resistance and oil resistance, and has problem in that they are severely damaged during printing, resulting in lowering of printing durability.